Electric brake systems of the above-mentioned kind are already known and are referred to also as brake-by-wire brake systems. The electric brake system includes several electric energy consumers such as at least one computer unit and a brake actuator for each wheel of the motor vehicle. By applying a switch-on signal, the energy consumers are connected to a voltage source so that the electric brake system is operational and is ready for braking operations. If a braking command is issued by a driver of the motor vehicle by applying foot force on a brake pedal, then the effect of the foot force on the pedal is detected by a sensor and is converted into an electric signal. The signal is then transmitted to the brake actuators and each brake actuator exercises, inter alia, a brake force on the wheel of the motor vehicle assigned thereto with the aid of an electric motor.
Electric brake systems of this kind can be considered as reliable especially because they are configured in two loops as are the conventional brake systems and therefore a channel is provided for each electric signal in each brake loop. If one of the signals is absent or one of the channels fails and if a brake loop thereby becomes inoperative, then the other brake loop remains operational and the electric brake system is operational to a limited extent. It is, however, noted that the switch-on signal is a one-channel signal. Accordingly, if the switch-on signal is absent (for example, because of a connector becoming separated or because of a break in a cable, which transmits the switch-on signal), then a complete failure of the entire electric brake system can occur (that is, both electric brake loops) and the motor vehicle can no longer be braked. The failure of the electric brake system is especially critical when the motor vehicle is otherwise operational and in movement. In summary, the failure of the switch-on signal can lead to a situation wherein the safe operation of the vehicle is affected and this is unacceptable.